The invention relates to an inductive transformer, in particular, a rotary transformer, for transmitting signals and/or energy between moving components and to a production method.
In the transmission of electrical signals and energy, for example to moving parts in a motor vehicle in conjunction with sensors mounted on the moving parts, it often becomes necessary, despite mechanical guidance problems, to establish a secure and yet flexible electrical or magnetic coupling between the moving parts. For instance in steering angle sensors for detecting the rotational angle of a steering wheel, major assembly and positional tolerances in the millimeter range, such as a play of approximately xc2x15 mm, exist between the rotatable steering spindle and the fixed steering column.
In the inductive transmission, known per se, of electrical energy and data from the steering column to the steering wheel in the motor vehicle, this play must also be preserved between the primary and secondary parts of the rotary transformer. As a rule, the result is relatively poor efficiency of the transmission.
Since the energy transmission in the cases described above can be on the level of approximately 1 watt if only the steering wheel electronics have to be supplied, and an additional 120 watts if a steering wheel heater is to be supplied, in such cases a winding spring is conventionally provided for data transmission and a wiper ring is conventionally provided for energy transmission. The winding spring and the wiper ring, however, in principle have a relatively high noise level and at the same time cause so-called EMC problems (EMC=electromagnetic compatibility).
According to the invention, an inductive transformer for transmitting measurement data and/or electrical energy between two components moving relative to one another, with one primary and one secondary transformer part is advantageously refined. In a gap that is necessarily created between the moving components, according to the invention a slide ring is provided, which comprises a plastic with embedded ferromagnetic metal parts.
The metal parts in the plastic are advantageously distributed in such a way that their proportion, on the end with which it is solidly disposed on one of the components, is high and becomes relatively slight toward the end with which it rubs against the respectively other component. Preferably, the metal parts are iron parts in the form of dust, chips or beads of tiny diameter, and the plastic is silicone or an elastomer with similar properties. This nonhomogeneity assures that in the sliding region, the abrasion is low because of the tiny proportion of iron parts, but the overall flux conductivity is improved.
An advantageous use is obtained in particular if one transformer part is mounted on the steering spindle of a vehicle, and another transformer part is mounted on the steering column of a vehicle, and then a transmission of measurement data and/or energy can be performed in a simple way, via the transformer parts.
It is also advantageously possible, in a method for producing an inductive transformer of the type defined above, to produce the slide ring by the following method steps. First, the homogeneous, flowable plastic filled with iron parts is placed in a mold for the contour of the slide ring. Then, by the intrinsic weight of the iron parts, sedimentation occurs, such that the iron parts are deposited in the region in which a high proportion is desired, and then the now-nonhomogeneous plastic hardens.
These and other characteristics of preferred refinements of the invention are disclosed not only in the claims but also in the description and the drawings; the individual characteristics can each be realized alone or in the form of subcombinations in the embodiment of the invention and in other fields and can represent both advantageous and patentable embodiments for which patent protection is here claimed.